Neural systems are organized to assimilate large amounts of sensory information and utilize it in making choices that result in meaningful behaviors. How such choices are made is central to understanding the function of any of these systems, whether they be complex processing centers such as the mammalian visual system or more simple invertebrate motor control systems. Several escape systems have served as useful models for studying this problem, because of various technical advantages which they offer. Although the neurons that make up an escape system must quickly process large amounts of sensory information in order to identify and react to a potential threat, the complete cellular analysis of the underlying circuitry is a very real possibility. The experiments described in this proposal are designed to take advantage of a particularly useful escape system, that of the american cockroach. The advantages of this system as a model include numerous large identifiable cells, (including the giant interneurons), and a resultant behavior that while reasonably complex is sufficiently predictable to allow extensive quantification. The recent discovery of a group of large thoracic interneurons that are post-synaptic to the giant interneurons means that a complete understanding of the decision making processes at the cellular level may now be possible. Our specific aims are to: (1) determine the manner in which directional sensory information carried in the giant interneurons is deciphered and used to control the directional escape movements, (2) determine the differences between two separate input pathways (the dorsal and ventral giant interneurons) and how one pathway is chosen over the other, and (3) determine the manner in which sensory information from thoracic appendages is used to influence the escape circuitry. All of these objectives will be pursued using intracellular analysis and dye injection techniques. Our hope is that these studies will generate principles regarding the manner in which nervous systems process sensory information and make meaningful decisions important to specific behaviors. Such principles may ultimately be generalized to more complex vertebrate systems which must solve similar problems.